1. Field of the Invention
The present invention relates to an underground mine roof supporting system and, more particularly, to a cable truss system.
2. Prior Art
Roof trusses, or roof support systems for mines, are well-known methods for providing support to the immediate roof strata. U.S. Pat. Nos. 4,946,315 and 5,018,907 disclose typical roof truss systems utilizing interconnected tie rods extending between rigid roof bolts. U.S. Pat. No. 5,415,498 discloses a mine roof support system utilizing a flexible cable in place of tie rods extending between rigid rock anchors or bolts.
Cable mine roof bolts have become popular due to several advantages over a more rigid rebar-type rock anchor. Cable bolts generally require a smaller diameter borehole, are easier to transport into the mine and easier to insert in applications with low seam height due to the bending of the cable. Additionally, cable bolts do not require couplings for long boreholes as rebar type rock anchors.
A variety of cable truss systems have been developed such as disclosed in U.S. Pat. Nos. 4,265,571; 5,462,391 and 5,466,095. U.S. Pat. No. 5,378,087 discloses a variety of mine roof support systems including systems utilizing cable mine roof bolts and more rigid rebar-type mine roof bolts. However, the difficulty with the above-described prior art cable mine roof trusses is that they do not provide cost-effective cable truss systems for a variety of applications. Much of the prior art requires highly specialized pieces, making the resulting truss system overly complicated, impractical and noneconomical to manufacture.